Method and apparatus for color print management

ABSTRACT

In a color printing environment, functions for printing color management are dissociated. An abstraction layer is also provided to facilitate setting and evaluation of all factors relating to color print and prediction.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a Divisional of U.S. patent application Ser.No. 13/843,768, METHOD AND APPARATUS FOR COLOR PRINT MANAGEMENT, filedMar. 15, 2013, the entirety of which is incorporated herein by thisreference thereto.

BACKGROUND OF THE INVENTION

Technical Field

The invention relates to color printing. More particularly, theinvention relates to color print management.

Description of the Background Art

State of the art color management systems try to solve all of thechallenges of color management in the context of printing in a fewoperations and with minimum color definition. However, a colormanagement workflow for printing must address the following operations:

-   -   Gamut adaptation between the source space and the printing        space;    -   Color separation strategy, especially if the color space has        more than three dimensions, such as CMYK;    -   Linearization for each ink to make response similar to a fixed        standard;    -   Ink limitations, such as maximum ink volume per channel and        in (n) dimensions of combinations per channel; and    -   Image and/or color adaptation, e.g. manual correction with        software or fixed correction with algorithmic functions and/or        look-up tables (LUT).

While some of the foregoing operations could be included in one colorLUT, such as an ICC profile, such technology is static. If it is desiredto change or make a dynamic gamut adaptation, then all of theseoperations must be separated.

Further, for all color printing processes, it is necessary to decomposethe color image information to be printed in each printing unit withrespect to:

-   -   The colorimetric inks, also referred to as primary colors; and    -   Print settings, such as frame sequence, support, finishing, etc.

Such decomposition of the color image is referred to as separation. Thebest known separation is CMYK (Cyan, Magenta, Yellow, Black), butseparation can also involve other primary colors, e.g. Blue, Brown,Yellow, Black, and/or involve more than four primary colors, e.g.Hexachrome C, M, Y, K, Orange, Green. The final expectations of theartist/client provide a good correspondence between the image to be usedfor printing, as validated before printing, and the image that resultsafter printing.

There are solutions that enable digital proofing, e.g. on paper, ofseparate files through a clear definition of colorimetric mixturelayers. Generally used technology involves the use of a look-up table(LUT) for storing values in a profile connection space (PCS), such asthe XYZ or CIELab color space, for example in an ICC color profile orequivalent. Each change in values of a layer in percentage (%) of inkhas a repercussion on the final color. To adjust the aesthetic image inthe context of its final result, it is common to change the channelvalues, e.g. CMYK, with editing software and visualization, for exampleby use of an editing program, such as Adobe Photoshop. In the CMYKspace, operators usually have experience doing this and the correctionis easy to understand because it is based on three primary colors andthe impact of such primary colors on complementary colors. For example,Red consists of Magenta and Yellow. Changing the Red, in turn, acts onthe information concerning Magenta and Yellow. For further example,clarity is often defined by the layer of Black and/or by the combinedaction of three layers trichrome (C, M, Y).

Changing the separation values, e.g. CMYK or nCLR (≥4 CLR) for aestheticreasons can lead to problems during printing. For example, the operatorcan increase the total ink (TIL: Total Ink Limit) and create problemswith drying and/or with the inks that are required. Thus, in the case ofuse of color away from traditional CMYK primaries, for example Blue,Red, Green, Yellow, the actions necessary to retouch the image aredifferent from those known by experience and the learning process islong and must be repeated for each new configuration of ink.

In the case of a separation of more than four colors (nCLR), for exampleusing as the four first colors, colors that are similar to those of theCMYK color space, even if the colors are different, the correction onseparate layers becomes very complex for the operator. For example, thecolor “flesh” in Hexachrome OG may involve Orange, Yellow, Magenta,Black, and Cyan. Inappropriate modifications of the Orange or Magenta orYellow layer can cause visible artifacts in the image.

Further, the color effect for data types that are achromatic such as,for example white ink for printing on a colored support, e.g. type Browncardboard; transparent varnish matt, gloss, satin, etc.; and metallicink, e.g. Silver ink, are not very easily visible if the separationalgorithm achieves results that are perceived as natural and qualitativeby the observer. For some creative operations, it may be necessary forthe creative work on, for example a virtual file as disclosed herein toview the presence, location, and quantity of a particular ink, i.e.Silver ink, before separation, given that the amount of this ink isautomatically calculated by subsequent separation technology, based oncolor information defined in the virtual space, combined with a strategyof color separation (CSS: Color Separation Strategy). Silver ink, forexample, when viewed at certain angles between the light and theobserver, is seen as having a color medium gray, as a gray ink of thesame color, but without the specular effect made by the metallicpigments. In virtual space—with only one image or with a static image—itis difficult, when visualizing a 2D image on a screen, to determine ifthe color medium gray is a shade of black ink or if it is a shade ofSilver ink.

Additionally, when the chromatic adaptation and management ofout-of-gamut colors, for example all the values that must be separated,are in gamut there is a unique relationship between a color of typeCIELab, XYZ, or equivalent and a space (n) dimension, i.e. if colors arein-gamut then there is a unique relationship between the deviceindependent color space (CIELab, XYZ) and colorants. Note that this isnot true if there are more than three colorants. Different CMYKcombinations can have the same CIELab or XYZ. However, for purposes ofthe invention herein, this is true in the disclosed virtual space. Theuse of an encoding of type LCh(Lightness/clarity-Chroma/Saturation-hue/tint) is in compliance with arepresentation of color space and can result from a number of decisionsbased upon experience or from analysis of colorimetric data. One problemcomes from the fact that it is difficult to establish relationships ofcolors, depending on the pigment inks, the color of the substrate, etc.,when the color source, working from data coded L*C*h, is an area of sizethat is variable and not constant.

Finally, for any printing process which has a post-printing operation(PPO), such as varnish, lamination, kiln, etc., the printer operator andthe customer cannot decide in advance of the PPO if the printing resultachieved after the PPO will be correct. In such case, all of theadjustments that concern color, e.g. density, dot gain, etc. are madeduring the printing process and give a visible result before the PPO.Usually, the PPO is not available immediately but, rather, is onlyavailable some hours or days afterward. However, the PPO typicallygenerates some color differences, e.g. kiln influences for ceramicsubstrates, or influences the human perception of the color, for exampledue a glossy difference. The customer wants to have a final production,i.e. after the PPO, in accordance with his artwork and/or physicalproof, based upon a visual comparison between the current print and thereference proof. Unfortunately, the printer proof only shows the finalresult, and not the result before the PPO.

SUMMARY OF THE INVENTION

Embodiments of the invention relate to dissociation of functions forprinting color management.

In another embodiment, an abstraction layer is used to facilitatesetting and evaluation of all factors relating to color print andprediction. Thus, an embodiment of the invention relates to the use of avirtual space, such as the virtual space for processing color matchingand editing.

An embodiment of the invention uses virtual space editing, referred toherein as “vRGB” (if used in RGB space). Virtual space allows full colorrepresentation of a file, as well as the representation of certaininfluences color inks and/or treatment, e.g. clear varnish.

An embodiment of the invention allows one to view this ink separately,thus generating a second virtual color profile, which contains only thecolor values relative to the ink concerned.

In another embodiment of the invention, the color values correspondingto a source from a known and defined space are matched to a predefinedtreatment. This embodiment of the invention thus establishes arelationships between the strategy of separation and the virtual colorvalues (stable) and can therefore establish algorithmically a uniquerelationship between the vLCh (virtual LCH) and (n)CLR data. It is thennecessary to establish a relationship [“3D to 3D”] between the actualmeasured (CIELab) colorimetric data and imaginary colorimetric data (orvirtual type vLCh) to establish the relationship with the source data.This relationship is established by a LUT with interpolation of the databetween the anchor points of the LUT. A 3D/3D LUT is therefore optimalin terms of precision/size/time, easy to achieve, and requires only onedata source, and does not require management of multiple (n)-dimensionspace-induced combinations. This vLCh space also has a single match [“3Dto 3D”] with the virtual editing space regardless of size.

In another embodiment of the invention, the result after printing ismeasured before any PPO. In this embodiment, a color definition, similarto an ICC profile, is created to show and proof the result that can beobtained by the PPO, when the customer and printer operator need todecide if the production could be validated before the PPO.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram showing a color management workflow accordingto the invention;

FIG. 2 is a flow diagram that shows the use of virtual space forprocessing color matching and editing according to the invention;

FIG. 3 is a block schematic diagram that shows a system making simple,reliable, and safe actions in retouching images possible while viewingthe color rendering after printing according to the invention;

FIG. 4 is a flow diagram that shows the use of visualizing a dedicatedlayer in virtual space according to the invention;

FIG. 5A is a block schematic diagram showing the state of the art withregard to visualization of special colors;

FIG. 5B is a block schematic diagram showing visualization of specialcolors according to the invention;

FIG. 6 is a flow diagram that shows the use of predictive virtual spaceaccording to the invention;

FIG. 7A is a block schematic diagram that shows a standard proofingprocess according to the invention;

FIG. 7B is a block schematic diagram that shows validation beforeproduction in a standard proofing process according to the invention;

FIG. 8A is a block schematic diagram that shows a predictive proofingprocess according to the invention;

FIG. 8B is a block schematic diagram that shows validation beforeproduction in a predictive proofing process according to the invention;

FIG. 9 is a flow diagram that shows multicolor separation by a virtualspace definition according to the invention;

FIG. 10 is a flow diagram that shows a proof before post-printingoperation according to the invention; and

FIG. 11 is a block schematic diagram that depicts a machine in theexemplary form of a computer system within which a set of instructionsfor causing the machine to perform any of the herein disclosedmethodologies may be executed.

DETAILED DESCRIPTION OF THE INVENTION

Dissociation of Functions for Printing Color Management

An embodiment of the invention relates to dissociation of functions forprinting color management. An embodiment thus provides a color workflow,in which separate and independent operator adjustment of operations isprovides, including setting gamut adaptation between a source space anda printing space; establishing a color separation strategy; effectinglinearization for each ink to make response similar to a fixed standard;adjusting for ink limitations, including maximum ink volume per channeland in (n) dimensions of combinations per channel; and effecting imageand/or color adaptation.

As discussed above, state of the art color management systems try tosolve all of the challenges of color management in the context ofprinting in a few operations and with minimum color definition. However,the above-described embodiment of the invention recognizes that a colormanagement workflow for printing must address the following operations:

-   -   Gamut adaptation between the source space and the printing        space;    -   Color separation strategy, especially if the color space has        more than three dimensions, such as CMYK;    -   Linearization for each ink to make response similar to a fixed        standard;    -   Ink limitations, such as maximum ink volume per channel and        in (n) dimensions of combinations per channel; and    -   Image and/or color adaptation, e.g. manual correction with        software or fixed correction with algorithmic functions and/or        look-up tables (LUT).

While some of the foregoing operations could be included in one colorLUT, such as an ICC profile, such technology is static. If it is desiredto change or make a dynamic gamut adaptation, then all of theseoperations must be separated.

Additional benefits are realized in a system which uses high-bitfloating point or fixed point data and math for high precision. ICCprofiles by their very nature are quantized and so introduce errors byinterpolation. Using an ICC profile for virtual viewing still has theseissues, but processing of the image data for production need not gothrough quantized lookup tables and can therefore be more accurate. Thisis particularly true when using a spectral model.

FIG. 1 is a flow diagram showing a color management workflow accordingto the invention. As can be seen from FIG. 1, each operation in a colormanagement workflow is separated. As shown in FIG. 1, print managementfunctions are divided between the color management function (CMF) 12,the CMF function or raster image processor function (RIP) 14, and theRIP function 16. Thus, an embodiment of the invention, for example,defines the color separation strategy (CSS) 43 as a standalone function,which is useful for virtual space and multicolor separation. Thoseskilled in the art will appreciate that the CSS can also be partially orentirely located in the CMF, RIP, or both the CMF and RIP.

As shown in FIG. 1, a device source 10, such as a file to be printed, isprovided to the CMF function. In an embodiment, the file is converted toa profile connection space (PCS), such as L*a*b* 40 with a ditheringoption 44 and A2B definitions 45 are applied, the A2B definitions beingany of static definitions from a look-up table (LUT) or matrix 21, ordynamic definitions from, for example, a spectral model 23.

Thereafter, gamut processing 41, image processing in a virtual space (asdiscussed below) 42, and the CSS 43 work together, i.e. are linked.Gamut mapping comprises a mapping function 46 which is determined, atleast in part, by any of the A2B, i.e. device to PCS (or color space),definition and an output space definition 25 (which is part of anoverall characterization 27); and a clipping function 47. While mappingand clipping take place together in some embodiments, with final mappingtaking place after clipping, in other embodiments clipping is performedfirst and, thereafter, mapping is performed, as in compression.

Image processing optionally includes an enhancement component 48 based,at least in part, upon an output space definition 25 (which is part ofan overall characterization 27).

The output of the CSS function then proceeds for further processing ateither a continuation of the CMF function or as part of the RIPfunction. Functions that are applied to the file can optionally includedot gain compensation 50, consideration of ink limitations 51, and bitdepth reduction 52, if appropriate, and subject to dithering 53.

The RIP function also applies, if necessary, a halftone function 60.

A device destination is determined 61 and a printed sample is produced62, which is used for the output characterization 27. Color perceptionis reviewed to meet human expectations 19 with regard to the output anda determination is made if corrections are needed 29. If corrections arerequired 30, then the particular function is adjusted. An importantfeature of the invention is the ability to adjust each of the severalprint workflow functions independently.

If corrections are not required, then the product is printed 31 aftervalidation of the first sample.

The herein disclosed color management workflow allows device developersto add their own gamut mapping algorithm into the workflow to customizethe color response of the device. Embodiments of the invention alsoallow the performance of some image processing with no dependency of thenumber of colors used by the color separation.

Virtual Space for Processing Color Matching and Editing

An embodiment of the invention relates to the use of a virtual space,such as the virtual space 42 shown in FIG. 1, for processing colormatching and editing. FIG. 2 is a flow diagram that shows the use ofvirtual space for processing color matching and editing according to theinvention. Thus, a method of processing color matching and editing isdisclosed that comprises inputting a source file for processing pursuantto printing 20. The source file is processed 22 in a reversible,three-dimensional virtual color space comprising a virtual workspacebetween said virtual color space and a printing space having “n” datasize of % separation (nCLR), where the % of each color is equivalent toa single virtual color having separation values necessary to obtain anexpected color rendering before separation into separate layers forprinting, wherein changing the % effects display of a resulting colorrendering. Thereafter, the processed source file is output for printing24.

As discussed above, for all color printing processes, it is necessary todecompose the color image information to be printed in each printingunit with respect to:

-   -   The colorimetric inks, also referred to as primary colors; and    -   Print settings, such as halftone, ink sequence, media,        finishing, etc.

Such decomposition of the color image is referred to as separation. Thebest known separation is CMYK (Cyan, Magenta, Yellow, Black), butseparation can also involve other primary colors, e.g. Blue, Brown,Yellow, Black, and/or involve more than four primary colors, e.g.Hexachrome C, M, Y, K, Orange, Green. The final expectations of theartist/client is to provide a good correspondence between the image tobe used for printing, as validated before printing, and the image thatresults after printing.

There are solutions that enable digital proofing, e.g. on paper, ofseparate files through a clear definition of colorimetric mixturelayers. Generally used technology involves a LUT to PCS (XYZ or CIELab),such as L*C*h or equivalent. Each change in values of a layer inpercentage (%) of ink has a repercussion on the final color. To adjustthe aesthetic image in the context of its final result, it is common tochange the channel values, e.g. CMYK, with editing software andvisualization, for example by use of an editing program, such as AdobePhotoshop. In the CMYK space, operators usually have experience doingthis and the correction is easy to understand because it is based onthree primary colors and the impact of such primary colors oncomplementary colors. For example, in printing, Red consists of mixingMagenta and Yellow. Changing the Red, in turn, acts on the informationconcerning Magenta and Yellow. For further example, clarity is oftendefined by the layer of Black and/or by the combined action of threelayers trichrome (C, M, Y).

Changing the separation values, e.g. CMYK or nCLR (≥4 CLR) for aestheticreasons can lead to problems during printing. Thus, an operator who isperforming a modification and/or adaptation in such color spaces musthave specific knowledge of the behavior of each and every ink that isused. Assuming that a particular ink is more opaque than another, it isnot possible to predict what results such modification and/or adaptationin a particular color space would produce on the output side. Inaccordance with an embodiment of the invention, an operator who performssuch modification and/or adaptation in the herein disclosed vRGB spaceeliminates the above discussed issues because the vRGB space includessuch knowledge already and the operator only changes RGB values and nota certain ink channel.

For example, the operator can increase the total ink (TIL: Total InkLimit) and create unwanted problems with drying and/or with the inksthat are required. Thus, in the case of use of color away fromtraditional CMYK primaries, for example Blue, Red, Green, Yellow, theactions necessary to retouch the image are different from those known byexperience and the learning process is long and must be repeated foreach new configuration of ink.

In the case of a separation of more than four colors (nCLR) and usingthe CMYK colors, even if the CMYK colors are different, the correctionon separate layers becomes very complex for the operator. For example,the color “flesh” in Hexachrome OG may involve Orange, Yellow, Magenta,Black, and Cyan. Inappropriate modifications of the Orange or Magenta orYellow layer can cause visible artifacts in the image and/or printingproblems.

Embodiments of the invention address the foregoing problems byseparating the objective, i.e. what is desired by the customer, from themeans, i.e. what can be achieved by the printer, by making simple,reliable, and safe actions in retouching images possible while viewingthe color rendering after printing (see FIG. 3). In this regard, it isnoted that all colors achievable by mixing inks (%) are measurable andquantifiable in a three-dimensional (3D) color space, e.g. CIELab, XYZ,etc.

FIG. 3 is a block schematic diagram that shows a system making simple,reliable, and safe actions in retouching images possible while viewingthe color rendering after printing according to the invention. In FIG.3, software for manipulating image device data 30 provides functions forcolor and image corrections 31 that include curves 26, levels 27, andcontrast 28. These corrections are applied to a device file in virtualspace 35.

The adjusted device file is provided to a color management module forvisualization of the file on a monitor 32, in which the device file isconverted to PCS 40 in accordance with an A2B definition 45, forexample, based upon static parameters from an LUT or matrix 21 and/ordynamic parameters from a spectral model 23. The PCS file is thenconverted to, for example, an RGB monitor color space 39 in accordancewith a B2A definition 38 that is based upon, for example, parameters inan LUT or matrix 37.

The file thus processed is provided to a monitor 34, where it can becompared with a reference 33 by a user to determine if the results meethuman expectations 19. If corrections are needed 29, then the processherein described is repeated, else the parameters thus determined areused in the color separation strategy 43.

In an embodiment of the invention there is a version of imaginary colorspace that is a surrogate for real color space. This version ofimaginary color space is easy to manipulate over the real version(color) of the file. Embodiments of the invention thus compriseestablishing a unique and reversible 3D or greater (nD), e.g. 4D, colorspace between the space and “n” data size of % separation (nCLR) andbetween the 3D color space and a virtual space % 3D. In such case, it ispossible to change the % to see the resulting color rendering, where the% of each color is equivalent to a single virtual color with theseparation values necessary for obtaining the expected color rendering.It is also possible with a 3D color space to see a change in % 4Dvirtual space, if any combination of the 4D space gives a uniqueresponse in a 3D space. Whatever the number of colors used in printing,in an embodiment the operator always works in a single 3D space, whichsimplifies learning. In addition, all the colors that the operator seesare easily printable, i.e. there is no out-of-gamut or excessive inkproblem. A key point in this embodiment of the invention is that the nDcolor space is hard to understand so it is mapped to a 3D virtual colorspace called vRGB and done in a way that makes it easy to understand.The gamut of this vRGB space is the same as the nCLR space. In someareas it is clipped (or flat) so that the user cannot edit to createcolors that cannot be reproduced on the nCLR device. That is, the vRGBspace enables WYSIWYG to the extent that the monitor gamut allows.

To be compatible with existing software in the market, e.g. AdobePhotoshop, an embodiment of the invention retains only the three spacedimensions that are not supported by Photoshop color, namely the RGBspace. \In an embodiment of the invention, the color space could also bea CMY (without K) space if supported by Photoshop. Thus, embodiments ofthe invention can also use the CMYK space without including the Blackchannel.

The invention establishes a unique relationship that is reversible, andit is also possible to convert the 3D virtual space into 4D spacevirtual and make it more in line with the features found in CMYKgraphics software.

By definition, the virtual space is not limited to a fixed number oflayers. Simply, all information and editing actions on virtual layersserve only to modify the color values and so, consequently, the valuesof separations required to obtain the final result.

The color display of the virtual space is effected by technology colormanagement, dynamic 23 (FIG. 1) or static type 21 (FIG. 1). The bestknown and most compatible to technology date is that of ICC profiles.Creation of an ICC profile with a table to Peripheral PCS (A2Bx) 45(FIG. 1) is performed in the virtual color space (3, 4, or more). Thiscolor space is used as virtual workspace for the creative. It istherefore necessary to convert (color matching operation) the colors ofthe source files (source space) in a virtual space which has the samecolor space as the (n) colors used for printing.

Thus, embodiments of the invention provide a virtual 3D space to (n)Dfor precise handling and simplified rendering of color after printing,whatever the dimension of the output space. Space conversion of thesource 10 (FIG. 1) in virtual space for discussion, editing, andproofing occurs before separation in separate layers for printing.

Visualizing Dedicated Layer in Virtual Space

FIG. 4 is a flow diagram that shows the use of visualizing a dedicatedlayer in virtual space according to the invention. This embodiment ofthe invention is related to the virtual space 42 for processing colormatching and editing embodiment, discussed above in connection withFIG. 1. Those skilled in the art will appreciate that this embodiment ofthe invention is also applicable for non-color values, such as glossvalue, specular value, etc. An embodiment of the invention uses virtualspace editing, referred to herein as “vRGB” (if used in RGB space).

In the embodiment of the invention shown in FIG. 4, a method forvisualizing a dedicated ink layer in a color is provided, in which avirtual color space is established 70; one or more virtual colorprofiles are generated, each of which only contains color valuesrelative to one of the two or more inks 71; one of the one or morevirtual color profiles is selected 72; and the selected virtual colorprofile is displayed in the virtual color space in relation to the color73. Thus, adjustment of the selected profile displays a visualization ofthe ink as modified by the adjustment.

Virtual space allows full color representation of a file, as well as therepresentation of certain influences color inks and/or treatment, e.g.clear varnish. The invention finds use for data types that areachromatic such as, for example:

-   -   White ink for printing on a colored support, e.g. type Brown        cardboard;    -   Transparent varnish matt, gloss, satin, etc.; and    -   Metallic ink, e.g. Silver ink.

The color effect of these parameters is not very easily visible if theseparation algorithm achieves results that are perceived as natural andqualitative by the observer. For some creative operations, it may benecessary for the creative work on the virtual file to view thepresence, location and quantity of a particular ink, i.e. Silver as acolor or specular effect, before separation, given that the amount ofthis ink is automatically calculated by subsequent separationtechnology, based on color information defined in the virtual space,combined with a strategy of color separation (CSS: Color SeparationStrategy). Silver ink, for example, is seen as having a color mediumgray, as a gray ink of the same color, but without the side specularmetallic pigments. In virtual space, it is impossible, when visualizingthe 2D image on a screen, to determine whether the gray is a shade ofblack ink or shade of ink Silver.

An embodiment of the invention allows one to view this ink separately,thus generating a second virtual color profile, which contains only thecolor values relative to the ink concerned. In contrast, the state ofthe art uses an N-profile for viewing specific channels, but currentlystandard applications do not support this kind of profile and its sizecan be quite large if it is to provide reasonable accuracy.

Accordingly, an embodiment of the invention allows one to view:

-   -   A specific ink separately, without the other inks/colors, to        validate the areas which are concerned, e.g. for silver,        varnish, and/or white inks;    -   The global rendering under another observer angle to see the        influence of the specular effect, e.g. for silver, varnish,        and/or other inks);    -   All of the other colors without the specific inks, to validate        the visual and color rendering without this additional ink.

Thus, an aspect embodiment generates a virtual color profile, whichcontains only the color values relative to a context previously defined.

This is accomplished either by a standard static LUT technology, such asan ICC profile, or by a dynamic technology LUT in which parameters areset by the user, on the basis of color data and/or spectro-colorimetricinformation, and by means of a plug-in and/or a dedicated application.By using this particular profile, e.g. under Adobe Photoshop (PSD), onecan directly visualize areas and nuances involved in the selected layer.With the invention, it is possible to generate and use as many desiredspecific virtual profiles in relation to the special colors that theuser wishes to see (see FIGS. 5A and 5B).

FIG. 5A is a block schematic diagram showing the state of the art withregard to visualization of special colors; and FIG. 5B is a blockschematic diagram showing visualization of special colors according tothe invention.

In FIG. 5A, the physical print process 79 involves printing a color 80,overprinting the color, for example with silver ink or varnish 81, andthe visual perception of the final result 82. The computer vision of theprint 84, based upon the visual perception of the final result asadjusted in 2D color space 85 produces the wrong mental perception 86.

In FIG. 5B, the physical print process 79 involves printing a color 80,overprinting the color, for example with silver ink or varnish 81, andthe visual perception of the final result 82. However, in an embodimentof the invention, the computer vision comprises a virtual space whichaccounts for the extra print layer 87, such that one visual perceptionof the final result 88 includes a virtual space for color 99 and anothervisual perception of the final result 90 includes a virtual space forthe overprinted color, here, silver 91. As a result, the print processproduces a good mental perception 92.

Predictive Virtual Space

FIG. 6 is a flow diagram that shows the use of predictive virtual spaceaccording to the invention. This embodiment of the invention is relatedto the virtual space 42 for processing color matching and editingembodiment, discussed above in connection with FIG. 1. An embodiment ofthe invention uses virtual space editing, referred to herein as “vRGB”(if used in RGB space).

FIG. 7A is a block schematic diagram that shows a standard proofingprocess according to the invention; and FIG. 7B is a block schematicdiagram that shows validation before production in a standard proofingprocess according to the invention.

In FIG. 7A, a device file in source space 10 is provided to a productionprocess 120, which performs operations of file processing 121, adaptingthe file for the print technology 122, and printing 123, resulting in aprint 124. When the file is adapted for the printing process and afterthe print is made, a characterization is performed 27 and, based upon anoutput space definition 119, a proofing process is performed 130.

The proofing process performs file processing 131 based upon the outputspace definition and the file as adapted for the print technology (118).After file processing, the file is adapted for the print 132 and sent tothe proofing printer 133, which produces a proof print 134. Humanvalidation 19 is provided for the print and the proof print.

In FIG. 7B, a device file in source space 10 is provided to a productionprocess 120, which performs operations of file processing 121, adaptingthe file for the print technology 122, and printing 123.

The proofing process performs file processing 131 based upon the file asadapted for the print technology. After file processing, the file isadapted for the print 132 and sent to the proofing printer 133, whichproduces a proof print 134. Human validation 19 is provided for theproof print. If the proof print is correct 125, the print is made 126.

FIG. 8A is a block schematic diagram that shows a predictive proofingprocess according to the invention; and FIG. 8B is a block schematicdiagram that shows validation before production in a predictive proofingprocess according to the invention.

In FIG. 8A, a device file in source space 10 is provided to a productionprocess 120, which performs operations of file processing 121, adaptingthe file for the print technology 122, and printing 123, resulting in aprint 124. After the print is made, a characterization is performed 27of the print and the device file (150). The characterization isprocessed to produce an output space definition 119, after which aproofing process is performed 130.

The proofing process performs file processing 131 based upon the outputspace definition of the print and the device file. After fileprocessing, the file is adapted for the print 132 and sent to theproofing printer 133, which produces a proof print 134. Human validation19 is provided for the print and the proof print.

In FIG. 8B, a proofing process 130 performs file processing 131 for thedevice file in source space 10. After file processing, the file isadapted for the print 132 and sent to the proofing printer 133, whichproduces a proof print 134. Human validation 19 is provided for theproof print.

Based upon the human validation (139) received at the entry point to aproductions process 140, the device file in source space 10 is providedto the production process 120, which performs operations of fileprocessing 121, adapting the file for the print technology 122, andprinting 123, resulting in a print 142, if validation is complete 141

In FIG. 6, an embodiment of the invention provides a method fornon-destructive visualization of a print file, in which a virtual colorspace is established 100; color values corresponding to a source fileare matched from a known and defined space to a predefined treatment inthe virtual color space 102; and a final color result is displayedbefore altering the file 104.

To get an accurate color display of the final print of a source file, itis necessary to process this file in all stages of color management. Forexample, visualization in virtual space RGB allows an accuraterepresentation of the final image but requires the availability ofsoftware technologies to achieve the necessary conversions of the sourcefile.

In an embodiment of the invention, the color values corresponding to asource from a known and defined space are matched to a predefinedtreatment. Thus, one can define a virtual profile that has applied to itsome treatment. The use of this profile lets one view that treatment ona source file of interest. When a virtual color space profile ismodified (or created with a treatment applied), it can be used to proofa source file in a non-destructive way, i.e. without changing the sourcefile itself. Using this definition color, e.g. ICC profile, it ispossible to view the final color result before any work on the file.This operation does not require particular expertise or modifying of theinformation contained in the source files in any way (non-destructiveactions), and is therefore very suitable for upstream decision process(Client, Graphic, Decider, etc.).

Multicolor Separation by a Virtual Space Definition

FIG. 9 is a flow diagram that shows multicolor separation by a virtualspace definition according to the invention. This embodiment of theinvention achieves a multicolor separation by use of a color separationstrategy (CSS) 43 (see FIG. 1), i.e. to set the relationship between thecolors. Such strategy, for example, does not use combinations that arenot interesting in terms of color space, e.g. Green mixed with Orange,and limits the ink overprint and total inks to facilitate the drying andthe mechanical resistance of printing, e.g. scraping, rubbing, unwantedrelief, resistance to the fold, etc.

In FIG. 9, an embodiment of the invention provides a method formulticolor separation of a print file containing source data, in which avirtual color space of constant size and constant form is established106; a relationship between a separation strategy and virtual colorvalues is established to effect a unique relationship between a virtualchannel vLCh (virtual LCh) and source data (n)CLR 108; and arelationship between actual measured colorimetric data and imaginarycolorimetric data or virtual type vLCh is established to establish therelationship with the source data 110. As such, the relationship isestablished by a look-up table (LUT) with interpolation of data betweenanchor points of the LUT.

Examples of such strategy include:

-   -   Local overlay: avoid overlaying Cyan+Yellow+Green if the        resulting hue is achievable by two primary colors instead of        three;    -   and    -   Total overlay: avoid overlaying the seven primary colors in        impressive seven colors, for 700% maximum ink to get the maximum        color space in terms of Colorimetry in CIE L*C*h coding within        the CIELab space.

Excluding the chromatic adaptation and management of colors that are outof gamut, e.g. all of the values that must be separated are in gamut,there is a unique relationship between a color of type CIELab, XYZ, orequivalent and space (n) dimension. The use of an encoding of type LCh(Lightness/clarity-Chroma/Saturation-hue/tint) is in compliance with arepresentation of color space and can result from a number of decisionsbased upon experience or from analysis of colorimetric data.

One problem concerns the fact that when a color source is working fromdata (coded L*C*h), it has an area of variable and non-constant size andgenerally much larger than the gamut of the nCLR device space, followingthe pigment inks, color support, etc. It is difficult to establishrelationships of colors if the dimension of the space and its form isconstantly variable. Accordingly, embodiments of the invention create acolor space abstract (virtual) which remains of constant size andconstant form and better fits to the gamut of the device space. Forexample, where:

-   -   Saturation is coded from 0 to 100 saturated shades as weakly        saturated. All the printed colors are quantified in Saturation        between 0 to 100, never more, never less, where 0 is        non-saturation or most weakly saturated and 100 is maximum        saturation; and    -   The Lightness of 0 to 100 unchanged from LCh hue of 0 to 360°        angle. All the printed colors are quantified in Lightness        between 0 to 100, even if the substrate is non-white or/and if        the darkest color is not so dark. Thus, in vLCh, L is always        between 0 to 100. The Darkest value is always 0, and the        Lightest value is always 100.

The invention thus establishes a relationship between the strategy ofseparation and the virtual color values (stable) and can thereforeestablish algorithmically a unique relationship between the vLCh(virtual LCh) and data (n)CLR. It is then necessary to establish arelationship [“3D to 3D”] between the actual measured (CIELab)colorimetric data and imaginary colorimetric data (or virtual type vLCh)to establish the relationship with the source data. This relationshipcould be established by a LUT with interpolation of the data between theanchor points of the LUT. A 3D/3D LUT is therefore optimal in terms ofprecision/size/time, easy to achieve, and requires only one data source,and does not require management of multiple (n)-dimension space-inducedcombinations. This vLCh space also has a single match [“3D to 3D”] withthe virtual editing space regardless of size.

Benefits of this approach include relating the strategy of colorseparation to the attainable color space by the combination of inks,media, print settings, and color relevant process conditions, e.g. thekiln process, lamination, etc. It is relative because it is insensitiveto the values of the colors themselves. For example, there can be a CSSbetween the vLCh and seven CLR inks, e.g. C, M, Y, K, O, Green, Blue,from the same virtual space. Values CIELab/XYZ necessary for theaccurate calibration and matching of color from the mixture of theseseven inks on a matte white surface are different from the CIELabvalues/XYZ obtained by mixing these seven inks on a glossy media withyellowish tone. This does not change the vLCh to 7CLR relationship, butonly changes the CIELab for the matte print media to vLCh and the CIELabrelationship for the brilliant cream base to vLCh. It is straightforwardto make or remake the calibration, while being assured that the strategyof separation is rigorously identical. Calibration, i.e. therelationship to vLCh CIELab, is also simplified because it is notnecessary to print a sample of all possible combinations of the nCLRspace, but only to print the combinations defined by the relationshipvLCh and (n) CLR.

If one considers that constant accuracy is not in %, then the number ofcombinations to print based on the number of dimension of the spaceyields the Table 1 below. Table 2 below shows image resolution inaccordance with a number of colors or dimensions of the color space.

TABLE 1 Number of colors (or dimension of the space) Number of colors(or dimension of the space) step % 3 4 5 6 7 8 9 10 2 100 8 16   32   64   128 256 512 1 024 5 25 125 625 3 125 15 625 78 125   4E+05 2E+06  1E+07 11 10 1E+03 1E+04 2E+05 2E+06 2E+07 2.14E+08 2E+09 2.59E+10

TABLE 2 Resolution number of colors (or dimension of the space)Resolution number of colors (or dimension of the space) Chart 3 4 5 6 78 9 10 1331 10.0% 19.8% 31.1% 43.2% 55.7% 68.6% 81.7% 95.0% 2000 8.6%17.6% 28.0% 39.2% 51.0% 63.1% 75.4% 87.8%

Because an A4 sheet, e.g. maximum measurable size by an automateddevice, can contain approximately 1500 to 2000 spots to the maximum, itcan be seen that 1331 spots ensures an accuracy for step variation of10% for a 3D space; and 1331 spots ensures an accuracy for stepvariation of ≈69% for a space 8D, 1/7^(th). To have a resolution similarto that of a 3D space, one should print and measure 214 million spots.It is therefore impossible to guarantee identical precision for 8CLR tothat of a 3CLR print without the use of a virtual space 3D vLCh. ButvLCh space is still in a 3D management space, and therefore optimal interms of accuracy/performance/low size of the calibration range.

For greater than three dimensions, management becomes complex andexpensive with regard to the number of combinations to manage (datavolume, time of processing, etc.). The increase in the number of dataalso increases the noise in the template data, and leads to inaccuraciesand visible artifacts. The state of the art solution is to lower theaccuracy by, e.g. reducing the number of grid points per dimension in aLUT. The use of the real color space is not convenient because of thevariable size in terms of clarity and saturation. Thus, by creating animaginary or virtual color space that has all the desired qualities,such as fixed dimension, of the real space resolution, etc., one caneasily fix the strategy of separation algorithmically between thisvirtual space and the dimensions in (n) output channels.

In a situation of calibration from the real space, rules are builtmanually or algorithmically to govern the relationship between theimaginary space and space (n) D. The calibration range is built in the3D imaginary space. This 3D range is converted to (n)D by various rules.The file (n)D is printed for colors in 3D real-time measurement. Acorrespondence is established between colorimetric values in real 3D andimaginary 3D space vLCh. This allows mapping the real space to theimaginary (3D to 3D) space and imaginary 3D space to (n)D in accordancewith the aforementioned rules for printing and determining the desired3D values.Formulae for Table 1:NberComb=(Steps)^(SpaceDim)  (1)where:

-   -   NberComb=the number of combinations;        Steps=the number of nodes in the space (equal distance), e.g.        Steps 3=0, 50, 100%;    -   SpaceDim=space dimension (3 to n)

$\begin{matrix}{{{Steps}\mspace{14mu}\%} = \left( {\left( 10^{(\frac{{lo}\;{g({NberComb}}}{SpaceDim})} \right) - 1} \right)^{- 1}} & (2)\end{matrix}$where:

-   -   Steps %=step in % of each node in the space (equal distance).

Proof Before Post-Printing Operation

FIG. 10 is a flow diagram that shows a proof before post-printingoperation according to the invention. An embodiment of the inventionmeasures the result expected after printing, but before any PPO, andcreates a color definition, similar to an ICC profile, to show and proofthe result. This allows the customer and printer operator to decide ifthe production could be validated before the PPO. In an embodiment, thelink between the color space before the PPO and after the PPO is definedby measuring the printing sample before and after PPO. A colorimetricfunction is applied to the data measured to simulate the phase beforeand after the PPO, for example to simulate saturation and/or increasingor decreasing contrast, yellowish variation of the media, etc. Amodification of the colorimetric values is then applied by interpolationin a color space, e.g. Lab, XYZ, spectral reflectance, density, etc.

In the embodiment of the invention in FIG. 10, a method for establishinga proof before a post-printing operation (PPO) is shown, in which aprocessor defines a link between a color space before the PPO and acolor space after the PPO by measuring a printing sample before the PPOand after the PPO 112; the processor applies a colorimetric function tothe measurement to simulate in a phase before the PPO a result in aphase after the PPO 114; and the processor applies the link tointerpolate values in the color space after the PPO to modify the colorspace before the PPO in accordance with the colorimetric function 116.

Computer Implementation

FIG. 11 is a block schematic diagram that depicts a machine in theexemplary form of a computer system 1600 within which a set ofinstructions for causing the machine to perform any of the hereindisclosed methodologies may be executed. In alternative embodiments, themachine may comprise or include a network router, a network switch, anetwork bridge, personal digital assistant (PDA), a cellular telephone,a Web appliance or any machine capable of executing or transmitting asequence of instructions that specify actions to be taken.

The computer system 1600 includes a processor 1602, a main memory 1604and a static memory 1606, which communicate with each other via a bus1608. The computer system 1600 may further include a display unit 1610,for example, a liquid crystal display (LCD) or a cathode ray tube (CRT).The computer system 1600 also includes an alphanumeric input device1612, for example, a keyboard; a cursor control device 1614, forexample, a mouse; a disk drive unit 1616, a signal generation device1618, for example, a speaker, and a network interface device 1628.

The disk drive unit 1616 includes a machine-readable medium 1624 onwhich is stored a set of executable instructions, i.e., software, 1626embodying any one, or all, of the methodologies described herein below.The software 1626 is also shown to reside, completely or at leastpartially, within the main memory 1604 and/or within the processor 1602.The software 1626 may further be transmitted or received over a network1630 by means of a network interface device 1628.

In contrast to the system 1600 discussed above, a different embodimentuses logic circuitry instead of computer-executed instructions toimplement processing entities. Depending upon the particularrequirements of the application in the areas of speed, expense, toolingcosts, and the like, this logic may be implemented by constructing anapplication-specific integrated circuit (ASIC) having thousands of tinyintegrated transistors. Such an ASIC may be implemented with CMOS(complementary metal oxide semiconductor), TTL (transistor-transistorlogic), VLSI (very large systems integration), or another suitableconstruction. Other alternatives include a digital signal processingchip (DSP), discrete circuitry (such as resistors, capacitors, diodes,inductors, and transistors), field programmable gate array (FPGA),programmable logic array (PLA), programmable logic device (PLD), and thelike.

It is to be understood that embodiments may be used as or to supportsoftware programs or software modules executed upon some form ofprocessing core (such as the CPU of a computer) or otherwise implementedor realized upon or within a machine or computer readable medium. Amachine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine, e.g. acomputer. For example, a machine readable medium includes read-onlymemory (ROM); random access memory (RAM); magnetic disk storage media;optical storage media; flash memory devices; electrical, optical,acoustical or other form of propagated signals, for example, carrierwaves, infrared signals, digital signals, etc.; or any other type ofmedia suitable for storing or transmitting information.

Although the invention is described herein with reference to thepreferred embodiment, one skilled in the art will readily appreciatethat other applications may be substituted for those set forth hereinwithout departing from the spirit and scope of the present invention.Accordingly, the invention should only be limited by the Claims includedbelow.

The invention claimed is:
 1. In a color management workflow, a methodfor separate and independent operator adjustment of operationscomprising: receiving a source file; using said source file to initiatea following iterative process: setting gamut adaptation between a sourcespace and a printing space; defining a color separation strategy;performing linearization for each ink to make response similar to afixed standard; adjusting for ink limitations, including maximum inkvolume per primary color channel of a plurality of primary colorchannels and per maximum number of combinations of the primary colorchannels; and effecting image and/or color adaptation by printing asample output file; determining whether a change is desired and if achange is desired, changing a setting and return to said setting gamutadaptation step, otherwise launching production based on the determinedgamut adaptation, the defined color separation strategy, the performedlinearization, and the adjustment for ink limitations.
 2. A method ofprocessing color matching and editing, comprising: receiving a sourcefile for processing pursuant to printing; creating a reversible,three-dimensional virtual color space that includes: a virtual workspacebetween a virtual color space and a printing space having a positiveinteger data size, the positive integer representing a number of primarycolors in the printing space, and wherein a percentage of ink of eachcolor is equivalent to a single virtual color having separation valuesnecessary to obtain an expected color rendering before separation intoseparate layers for printing, wherein changing the percentage effectsdisplay of a resulting color rendering; using at least ink data fromsaid source file to initiate a following iterative process: processingink using in said reversible, three-dimensional virtual color space;printing a sample processed source file based on the processed ink;determining whether a change is desired to the sample processed sourcefile and if a change is desired, changing a percentage of ink and returnto said processing ink step, otherwise launching production based on theprocessed ink.
 3. A method for multicolor separation of a print filecontaining source data, comprising: receiving a print file containingsource data; creating a virtual color space of constant size andconstant form; using said source data to initiate a following iterativeprocess: defining a relationship between a separation strategy andvirtual color values including defining a unique relationship between avirtual channel vLCh (virtual CHL) and said data; obtaining actualmeasured colorimetric data; defining a relationship between said actualmeasured colorimetric data and imaginary colorimetric data or virtualtype vLCh and codifying said relationship in a look-up table (LUT) withinterpolation of data between anchor points of the LUT; performingmulticolor separation of the print file using said LUT withinterpolation of data between anchor points of the LUT; printing asample output file; and determining whether a change is desired and if achange is desired, changing a setting and return to said defining arelationship step, otherwise launching production based on the codifiedLUT with interpolation of data between anchor points of the LUT.